Water is coming out of outside hook up..

you could also replace the check valve with a good quality ball valve and add one the discharge of the water pump. you'd probably get more water flow too

you just have to remember to switch them when going from city water to tank water

Here is an easy way to take care of the problem until you can fix the check valve. Any good hardware store should have one.

They can be repaired for free. I have done this when winterizing and bleed the valve with too much pressure on it. An oring unseats and causes the leak.
http://www.sunlineclub.com/forums/f71/fresh-water-inlet-valve-repair-11736.html

I had a very similar experience during my last camping trip. I hooked up the water hose to the city water connection, and after a short while, water was gushing out from the breather hole adjacent to the gravity fill inlet. Somehow, my fresh water tank filled up while I was connected to the city water connection.

I assumed a check valve somehwere had failed so I called an RV tech friend and explained the situation to him over the phone. He told me the check valve is buil into the water pump and I would have to replace the entire unit. Is he right, or do I have a separate check valve somewhere in the system? To be fair to the RV tech friend, he is not familiar with my TT and has never worked on it. It's worth mentioning that prior to this experience the pump was coming on for a couple of seconds every so often when I was dry camping.

You can't replace just the check valve in a city water inlet because the inlet and check valve are a one-piece assembly.

Providing the check valve isn't really plugged up and blocking flow, one way to permanently fix this (rather than replace the inlet) is to add a new check valve to the interior side of the city water inlet. You'll need access to the rear of the inlet and usually can be reached. Go to a plumbing store and get an inline 1/2" brass check valve. Not sure if Lowes or HD will have them. City water inlets have a standard 1/2" pipe thread so you can just screw the new one in place. You may need a short nipple too. If the existing check valve seems to be plugged up, you can punch it out (I've done it before).

You might want to inspect the check valve at the FW pump too. Ours was leaking water back into the FW tank. We never use our FW tank and about a year after we bought the TT, I discovered the tank was filling up.

A quick fix is to connect up a water hose with a hand held spigot on it... Or pick up a plug cap with the right mating thread on it and just cap it off...

There is an one way value either at the outside city water connection or just inside the trailer a few inches...

sometime debress gets into the one way valve and they won't close properly...

When you are connected to city there is no reason to have your tank water pump ON... The city water pressure will be all you need to move the fresh water around your trailer...

I only use my on-board water pump when camping off grid to use water from the fresh water tank which with my older camper I have to manually fill.

Roy Ken

Thanks! Pushed in on check valve and it set back in place.. but not before I got a face full water lol! Glad I had glasses on ;-)

Probably need to replace your back-flow preventer valve.

There's a spring loaded check valve in the city water connection. It may be stuck open. Stick something (finger, handle of a butter knife, ink pen, etc) in there to open and close that valve a few times. Be gentle, so as not to break the valve.

You'll need to remove the screen to get at it.